The disclosure of Japanese Patent Application No. 2001-354815 filed on Nov. 20, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a pulsation damping device in a fuel pump module in a fuel tank, in particular, the pulsation damping devise which prohibits generation of an abnormal noise such as a valve hit noise caused by a fuel pressure control valve due to pulsation of a fuel discharged from the fuel tank.
2. Description of Related Art
A fuel in a fuel supply system is discharged from a fuel tank by a delivery force of a fuel pump of a pump module disposed in the fuel tank (hereinafter referred to as a fuel pump). Next, the fuel is filtered by a fuel filter and injected through a fuel injector toward a combustion chamber of an internal combustion engine. Further, a fuel pressure control valve is disposed downstream of the fuel filter for the purpose of adjusting a pressure of the aforementioned injected fuel.
In the aforementioned fuel supply system, the fuel pump and the fuel filter and the like are installed in the fuel tank for the purpose of simplifying the structure and reducing an effect of the heat.
FIG. 9 is a vertical sectional view showing a fuel pump module A which is a related art of the invention, and FIG. 10 is a horizontal sectional view of the same.
Hereinafter a structure of the fuel pump module will be explained. The fuel pump module A is provided with a fuel pump B, a fuel filter C downstream of the fuel pump B, a flow-out chamber D in the fuel filter C, and a discharge pipe E continuously formed with the flow-out chamber D.
Moreover, a fuel pressure control valve F is attached to an adjacent portion to the flow-out chamber D in order to adjust a pressure of a fuel supplied from the discharge pipe E to an engine combustion chamber to a predetermined value.
The fuel pump module A with the aforementioned structure applies the fuel with pulsation by means of rotation of a motor in the fuel pump B, which is a driving source. Next, the fuel applied with pulsation is discharged, as it is, to the combustion chamber through the discharge pipe E.
Moreover, the pulsation is amplified by passing of the fuel in a filter element G of the fuel filter C. Further, when the fuel containing the aforementioned pulsation component is transmitted to the fuel pressure control valve F, the fuel pressure control valve F acts as a resonate body so as to further amplify the pulsation. This sometimes causes generation of an abnormal noise such as a valve hit noise from the fuel pressure control valve F.
It is therefore an object of the invention to provide a pulsation damping device in a fuel pump module that inhibits generation of an abnormal noise such as a valve hit noise, by forming pulsation damping means in a transmission passage of a fuel between a fuel pump and a fuel pressure control valve.
In order to accomplish the aforementioned object, a pulsation damping device according to an aspect of the invention is provided with a fuel pump for sucking and discharging a fuel in a fuel tank, a fuel filter downstream of the fuel pump for removing a foreign matter in the fuel, and a fuel pressure control valve for adjusting discharge of the fuel that flowed out from the fuel filter to the combustion chamber. Furthermore, a damping portion for damping pulsation of the fuel is provided between the fuel filter and the fuel pressure control valve. In particular, the damping portion is provided between a flow-out chamber formed at downstream of a filter element in the fuel pump and a fuel pressure control valve which is an adjacent portion to the flow-out chamber.
The damping portion may be a buffer wall formed in a supply conduit continuously formed with the flow-out chamber via a communication hole in a side wall of a filter case so as to form a branch passage to a supply pipe to an engine combustion chamber and to the fuel pressure control valve.
Further, the damping portion may be a conduit disposed in the flow-out chamber. One end portion of the conduit is opened in the flow-out chamber, and other end portion thereof is opened in the supply conduit continuously formed via a communication hole in the side wall of the filter case.
Moreover, the aforementioned damping portion may be a fuel passage formed in the flow-out chamber. The flow passage is a fuel flow passage formed by a first circular separation wall, having a notch portion at a part thereof, for dividing a substantially circular space, and a second separation wall, having a notch portion at a part thereof, at a position opposite to the notch portion of the first separation wall and having a larger diameter than the first separation wall, and being formed outside of the first separation wall with a predetermined distance therefrom. The flow passage is communicated with the supply conduit.
Further, the damping portion may be a curved vertical wall formed to the front of a communication hole in the side wall of the filter case at the bottom of the flow-out chamber. The length of the vertical wall is larger than a width of an opening portion of the communication hole, and the vertical wall is formed along the inner wall of the filter case with a predetermined distance therefrom.
Moreover, objects of the invention may be accomplished by combining a plurality of specific pulsation damping portions with various structures as above.